1. Field of the Invention
The present invention relates to an optical disk apparatus for recording information on an information recording medium by using semiconductor laser.
2. Description of the Related Art
Optical disks of recording data include a write once type optical disk capable of recording data only once (CD-R, DVD-R, DVD+R and the like) and a rewritable type optical disk capable of rewriting data (CD-RW, DVD-RAM, DVD-RW, DVD+RW and the like).
In the case of the write once type optical disk, a recording layer made up of an organic dye is irradiated by a laser beam to change its property, thus forming pits thereon to record data. On the other hand, in the case of the rewritable type optical disk, data is rewritten by the reversible change of the recording layer called the phase change. More specifically, the irradiation of high-power laser beam on the recording medium and quenching effect cause it to be transformed into the amorphous state, while the irradiation of medium-power laser beam on the recording medium and slow cooling effect cause it to be transformed into the crystalline state. Thus, this phase change makes data to be recorded or erased.
When recording an optical disk, the recording conditions are scattered depending on combination of the optical disk and optical disk apparatus used for the recording. For example, they depend on the external environments such as temperature and humidity, the characteristics of the recording films of optical disks, and the mechanical characteristics such as groove shape and warpage of disk. Some optical disk apparatuses incorporate an adjustment method for reducing these scattering effects.
For example, there is an optical disk apparatus that has a function to adjust the recording laser power called OPC (Optimum Power Control). This method is to write as a test on a laser power adjusting region or a PCA (Power Calibration Area) provided on each optical disk and to determine the optimum laser power in each recording condition from the vertical asymmetry of the reproduction result from this area (for example, referring to JP-A-2002-175624 and JP-A-2002-298356).